1. Field of the Invention
The present invention is related to an image forming apparatus configured to adjust the amount of light exposed by an exposure unit.
2. Description of the Related Art
An image forming apparatus according to the related art using the electrophotographic method forms an electrostatic latent image on a photosensitive drum by exposing light onto the photosensitive drum serving as an image bearing member by an exposure unit. The image is formed by transferring developer (toner image) formed on the photosensitive drum by developing the electrostatic latent image to a sheet of paper as the recording medium. The light source serving as the exposure unit can be a laser, light-emitting diode (LED), or other light source.
According to such an image forming apparatus, uneven density occurs in the developer formed on the photosensitive drum when the laser scans in the main scanning direction (longitudinal direction of the photosensitive drum). Examples of uneven density include uneven exposure amounts, unevenness in the sensitivity of the photosensitive drum, differences in the charge amount of the developer, and other like unevenness due to the developing unit. To reduce this uneven density, Japanese Unexamined Patent Application Publication No. 2009-98626 proposes an invention to form toner patches for detecting uneven density, and adjusting the maximum exposure amount profile for the laser in the main scanning direction on the basis of the result of detecting the uneven density levels of the toner patch. In this case, the maximum exposure amount of the laser is the amount of light used when forming an image at a uneven density level of 100% (solid image). By adjusting the maximum exposure amount, uneven density can be reduced, including halftones in the main scanning direction. Adjustments to the maximum exposure amount of the laser are performed by dividing the laser scanning region of the main scanning direction into multiple smaller regions, and adjusting the maximum exposure amount for each of the divided scanning regions.
According to the related art, uneven density is reduced by dividing the laser scanning region for the main scanning direction into multiple smaller regions, and adjusting the maximum exposure amount. In this case, by increasing the number of the divided scanning regions, uneven density can be further reduced as the maximum exposure amount can be adjusted more finely.
However, by dividing the laser scanning region into multiple smaller regions, time is required to change the maximum exposure amount profile of each scanning region. The adjustments of the laser maximum exposure amount are performed sequentially for each region, and so the time required for changing increases as the amount of scanning regions increase. As a result, this creates a problem in which downtime required for forming toner patches for detecting uneven density, and performing recalibration to adjust the maximum exposure amount profiles in the main scanning direction on the basis of the results of detecting uneven density levels of the toner patches increases.